With the advancement of national dual-carbon targets, the large-scale integration of renewable energy sources has significantly increased the proportion of power converters in modern power grids. This trend introduces oscillation issues that reduce system disturbance resistance and increase design complexity. To investigate power grid resilience against disturbances, this paper proposes a voltage-power harmonic modeling methodology for converters and transmission lines, along with an aggregation approach for multi-converter systems. Compared with traditional impedance/admittance methods, our voltage magnitude/phase and active/reactive power disturbances maintain frequency consistency without inducing frequency variations, thereby avoiding the physical significance loss inherent in conventional impedance-based approaches. Furthermore, frequency-sweep verification was conducted on the developed voltage-power model. Stability analysis using this model was performed and validated through simulation experiments, demonstrating the effectiveness and accuracy of the proposed methodology in electrical engineering applications.